Particle categorization

ABSTRACT

An example system includes an input channel having a first end and a second end to receive particles through the first end, a sensor to categorize particles in the input channel into one of at least two categories, and at least two output channels Each output channel is coupled to the second end of the input channel to receive particles from the input channel, and each output channel is associated with at least one category of the at least two categories. Each output channel has a corresponding pump operable, based on the categorization of a detected particle in a category associated with a different output channel, to selectively slow, stop, or reverse a flow of particles into the output channel from the input channel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Utility Patent Application is a U.S. National Stage filing under 35U.S.C. § 371 of PCT/US2018/015783, filed Jan. 29, 2018, incorporated byreference herein.

BACKGROUND

Microfluidic devices are increasingly commonplace in a variety ofenvironments. For example, microfluidic devices have applicability inbiology, medicine, genetics and numerous other fields. Microfluidicdevices may include such devices as lab-on-a-chip micro-total analyticalsystems and can carry, analyze, or process various particles, bacteria,biological cells and other solid and soft objects of microscale. Variousmicrofluidic devices may include fluids flowing through narrow channels.In a lab-on-a-chip, for example, blood cells may be moved from onechamber to another, such as from an input port to a reaction chamber. Inother examples, the microfluidic device may be provided for the flow ofother fluids or materials, such as blood or other biological fluids.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of various examples, reference is nowmade to the following description taken in connection with theaccompanying drawings in which:

FIG. 1 illustrates an example system for categorization of particles;

FIGS. 2-6 illustrate an example categorization of particles using theexample system of FIG. 1 ;

FIG. 7 illustrates another example system for categorization ofparticles;

FIG. 8 illustrates another example system for categorization ofparticles;

FIG. 9 illustrates another example system for categorization ofparticles;

FIG. 10 illustrates another example system for categorization ofparticles;

FIG. 11 illustrates another example system for categorization ofparticles;

FIG. 12 illustrates another example system for categorization ofparticles;

FIG. 13 illustrates another example system for categorization ofparticles;

FIG. 14 is a schematic illustration of an example system forcategorization of particles;

FIG. 15 is a flowchart illustrating an example method;

FIG. 16 illustrates a block diagram of an example system with acomputer-readable storage medium including instructions executable by aprocessor for particle categorization;

FIG. 17 illustrates example pumps of a system for categorization ofparticles; and

FIG. 18 illustrates another example pumps of a system for categorizationof particles.

DETAILED DESCRIPTION

As noted above, microfluidic devices may be provided to flow fluidsthrough narrow channels to, for example, reaction chambers. In variousexamples, the fluids may include any number of particles within a flow.A reaction chamber or another output of the channels may use theparticles in a separated or concentrated condition. Accordingly, thevarious particles in a flow are separated (e.g., sorted or categorized)for use within the microfluidic device or for output from themicrofluidic device.

In order to separate the particles, some devices use a valve to open acorresponding channel to direct a particle into an appropriate channel.Such valves typically result in slowing of the flow upstream of thevalve. Further, such valves have the potential to fail, resulting infailure of sorting in all output channels.

Further, categorizing or flow of particles may be facilitated with theuse of pumps. While any of a variety of pumps may be used, externalpumps (e.g., syringe pumps or capillary pumps) may increase complexityand expense by requiring a pump to be outside the lab-on-a-chip, forexample.

Various examples described herein relate to categorizing and/or sortingof particles in, for example, a microfluidic device. A flow of particlescontaining at least two categories of particles is sorted by directingeach particle from an input channel to one of at least two outputchannels, each output channel corresponding to a different category. Asensor in the input channel can detect a particle, which may beidentified as belonging to a particular category, either by the sensoritself or another processor or controller. Each output channel isprovided with a pump, such as an inertial pump. Activation of the pumpin a particular output channel causes flow in that channel to be slowed,stopped, or reversed. Thus, flow from the input channel is directed awayfrom the output channel with the activated pump. Based on the detectionof the particle by the sensor in the input channel, the pump in eachoutput channel not corresponding to the category of the detectedparticle, or corresponding to a category that is different than thecategory of the detected particle, is activated. Thus, flow is slowed,stopped, or reversed in output channels corresponding to a differentcategory than the category of the detected particle, and the detectedparticle is directed into the output channel corresponding to itscategory. Further, in various examples, each pump may be an inertialpump that is integrated within the device, such as within acorresponding channel,

Referring now to the Figures, FIG. 1 illustrates an example system forcategorizing, or sorting, of particles. The example system may be any ofa variety of devices, such as microfluidic devices, lab-on-a-chip, ormicro total analytical systems, for example. Accordingly, while theexample system 100 may be described in the microfluidic context, inother examples, the example system 100 may include a system forcategorizing larger particles than those found in the microfluidicenvironment. In the example of FIG. 1 , the example system 100 includesan input channel 110 with a first end 112 and a second end 114. Theinput channel 110 may receive particles therein through the first end112. An arrow in the input channel 110 illustrated in FIG. 1 indicatesthe direction of flow of the particles. As noted above, the particlesmay include any of a variety of particles such as, but not limited to,blood cells. In various examples, the input channel 110 may be a longand/or narrow channel.

In various examples, the example system 100 is a microfluidic device,and the input channel 110 is a microfluidic channel. In one example, theinput channel 110 has a cross-sectional width of between about 10 μm andabout 500 μm. Various examples of the system 100 may be formed byperforming various microfabrication and/or micromachining processes on asubstrate to form and/or connect structures and/or components. Thesubstrate may comprise a silicon based wafer or other such similarmaterials used for microfabricated devices (e.g., glass, galliumarsenide, plastics, etc.). Examples may comprise microfluidic channels,fluid actuators, and/or volumetric chambers. Microfluidic channelsand/or chambers may be formed by performing etching, microfabricationprocesses (e.g., photolithography), or micromachining processes in asubstrate. Accordingly, microfluidic channels and/or chambers may bedefined by surfaces fabricated in the substrate of a microfluidicdevice. In some implementations, microfluidic channels and/or chambersmay be formed by an overall package, wherein multiple connected packagecomponents that combine to form or define the microfluidic channeland/or chamber.

In the example of FIG. 1 , the example system 100 includes a sensor 120.In various examples, the sensor 120 may be selected from any of avariety of types of sensors. For examples, the sensor 120 may include,but not limited to, an electrical current sensor, an impedance sensor,an optical sensor, magnetic, imaging, or a thermal sensor. The sensor120 of the example system 100 is provided to categorize particles in theinput channel 110 into one of at least two categories. For example, astream of particles flowing through the input channel 110 may includetwo, three, or more different categories of particles. In variousexamples, the categories of particles may include, but not limited to,solid particles, soft particles, gas bubbles, biological cells, dropletsof fluid (e.g., immiscible fluid, also referred to as colloidalparticles), and clusters thereof. A category may include a particulartype of particle or a group of types of particles. For example, in oneexample, a category may include all blood cells, and in another example,a category may include a particular type of blood cell. In one example,the sensor is positioned to allow detection of a particle andidentification of at least one parameter associated with the particlewhich allows categorization of the particle.

The example system 100 further includes at least two output channels 130a, 130 b that are coupled to the second end 114 of the input channel 110to receive particles from the input channel 110. In the exampleillustrated in FIG. 1 , a flow of particles in the input channel 110forks into one of the two output channels 130 a, 130 b. The arrows inthe output channels 130 a, 130 b in FIG. 1 indicate the direction offlow of the particles in the output channels 130 a, 130 b. In variousexamples, the input channel 110 may be coupled to any practical numberof output channels 130, such as three, four, or more output channels.Each output channel 130 a, 130 b is associated with at least onecategory of the at least two categories. For example, in one example,the flow of particles through the input channel 110 includes particlesbelonging to category A and category B. In the example of FIG. 1 , oneoutput channel 130 a is associated with category A, and the outer outputchannel 130 b is associated with category B.

In the example system 100 of FIG. 1 , each output channel 130 a, 130 bis provided with a corresponding pump 140 a, 140 b. In the example inwhich the example system 100 is a microfluidic device, each pump 140 a,140 b may be an inertial pump. As used herein, an inertial pumpcorresponds to a fluid actuator and related components disposed in anasymmetric position in a microfluidic channel, where an asymmetricposition of the fluid actuator corresponds to the fluid actuator beingpositioned less distance from a first end of a microfluidic channel ascompared to a distance to a second end of the microfluidic channel.Accordingly, in some examples, a fluid actuator of an inertial pump isnot positioned at a mid-point of a microfluidic channel. The asymmetricpositioning of the fluid actuator in the microfluidic channelfacilitates an asymmetric response in fluid proximate the fluid actuatorthat results in fluid displacement when the fluid actuator is actuated.Repeated actuation of the fluid actuator causes a pulse-like flow offluid through the microfluidic channel.

In some examples, an inertial pump includes a thermal actuator having aheating element (e.g., a thermal resistor 1710, as shown in FIG. 17 forexample system 101) that may be heated to cause a bubble to form in afluid proximate the heating element. In such examples, a surface of aheating element (having a surface area) may be proximate to a surface ofa microfluidic channel in which the heating element is disposed suchthat fluid in the microfluidic channel may thermally interact with theheating element. In some examples, the heating element may comprise athermal resistor with at least one passivation layer disposed on aheating surface such that fluid to be heated may contact a topmostsurface of the at least one passivation layer. Formation and subsequentcollapse of such bubble may generate circulation flow of the fluid. Aswill be appreciated, asymmetries of the expansion-collapse cycle for abubble may generate such flow for fluid pumping, where such pumping maybe referred to as “inertial pumping.” In other examples, a fluidactuator corresponding to an inertial pump may comprise a membrane (suchas a piezo-electric membrane 1810, as shown in FIG. 18 for examplesystem 102) that may generate compressive and tensile fluiddisplacements to thereby cause fluid flow.

Of course, in other examples, any of a variety of other types of pumpsmay be used. Each pump 140 a, 140 b is operable, based on thecategorization of a detected particle (e.g., by the sensor 120), toselectively slow, stop, or reverse flow of particles into the outputchannel 130 a, 130 b from the input channel 110. In this regard, thepump 140 a, 140 b may pump a fluid in a direction opposite the directionof the flow of particles from the input channel 110. The rate of pumpingof the fluid by the pump 140 a, 140 b may be sufficient to slow, stop,or reverse the flow from the input channel 110.

In various examples, the input channel 110 and each output channel 130a, 130 b are microfluidic channels. In this regard, the input channel110 and the output channels 130 a, 130 b may have a cross-sectionalwidth of between about 10 μm and about 500 μm, for example.

Referring now to FIGS. 2-6 , an example categorizing of particles usingthe example system 100 of FIG. 1 is illustrated. Referring first to FIG.2 , a flow of particles 200 is illustrated flowing through the inputchannel 100. The term “particles” is used herein to refer to any of avariety of objects including, but not limited to, solid particles, softparticles, gas bubbles, biological cells, droplets of fluid (e.g.,immiscible fluid, also referred to as colloidal particles, or theiragglomerates), and clusters thereof. As noted above, the direction ofthe flow is indicated by the arrow, as left to right in FIG. 1 . Theflow of particles 200 includes particles belonging to at least twocategories. In the example illustrated in FIGS. 2-6 , the flow includesparticles in two categories, category A and category B. The particlesbelonging to category A are illustrated as open circles 210, and theparticles belonging to category B are illustrated as closed circles 220.In one example, the example system 100 may operate to provide aconcentration of one particle. In this regard, the desired particle maybe indicated as category A and may be directed to a reservoir to holdthe particle in a concentrated form. Category B may indicate all otherparticles in the flow 200, which may be considered waste, and may bedirected to a waste chamber.

Referring now to FIG. 3 , a particle 212 reaches a point in the inputchannel 110 where it is detected by the sensor 120. The sensor 120 maydetect not only the presence of the particle 212 in a detection zone,for example, of the input channel 110, but may also detect acharacteristic of the particle which allows categorization of theparticle 212 into one of the set of categories (e.g., category A orcategory B). Such characteristics may include any of a variety ofparameters, such as size, shape, dielectric constant, electricpolarizability, magnetic susceptibility, magnetic moment, opticalrefractive index, color, luminescence, thermal capacitance, and thermalconductivity, for example. In various examples, the sensor 120 itselfmay categorize the particle 212 based on the detected characteristic, orthe sensor 120 may provide a signal to a controller indicating thedetected characteristic for the controller to perform thecategorization. In the example illustrated in FIG. 3 , the detectedparticle 212 is characterized as belonging to category A.

Referring now to FIG. 4 , based on the categorization of the particle212 in category A, pumps corresponding to all output channels that arenot associated with category A are actuated. In other words, pumpscorresponding to all output channels that are associated with adifferent category than the identified category of the particle 212 areactuated. In the example of FIG. 4 , output channel 130 a is associatedwith category A, and output channel 130 b is associated with category B.Accordingly, the pump 140 b corresponding to output channel 130 b isactuated, as illustrated by the bold outline of pump 140 b in FIG. 4 .The actuation of the pump 140 b causes the flow into output channel 130b to slow, stop, or reverse, as indicated by the removal of the arrowcorresponding to the output channel 130 b in FIG. 4 .

In various examples, the flow of the particles 200 may include a fluidwhich carries the particles 200 through the channel. The fluid may be agas or a liquid, for example. In one example, the particles are solid orliquid particles, and the pumps 140 a, 140 b are inertial pumps. Invarious example, the actuation of the pump may cause the pump to force asimilar or identical fluid in a direction opposite the flow from theinput channel 110. This flow caused by the pump 140 b serves to stop,slow, or reverse the flow from the input channel 110. As illustrated inFIG. 4 , this causes the particle 212 to flow into the output channel130 a corresponding to the category (category A) associated with theparticle 212.

Referring now to FIG. 5 , the flow of particles 200 in the input channel110 continues with another particle being detected by the sensor 120. Inthe example of FIG. 5 , the next particle 222 belongs to category B (asindicated by the closed circle). Based on the categorization of theparticle 222 in category B, pumps corresponding to all output channelsthat are associated with a category that is different from category Bare actuated. As illustrated in FIG. 6 , the pump 140 a corresponding tooutput channel 130 a, which is associated with category A, is actuated,as illustrated by the bold outline of pump 140 a in FIG. 6 . Theactuation of the pump 140 a causes the flow into output channel 130 a toslow, stop, or reverse, as indicated by the removal of the arrowcorresponding to the output channel 130 a in FIG. 6 . The particle 222is thus directed into the appropriate output channel 130 b correspondingthe categorization of the particle 222 into category B.

As noted above, in various examples, the pumps corresponding to alloutput channels that are associated with a category that is differentfrom the identified category are actuated to slow, stop, or reverse flowin those channels. For example, with reference to FIG. 6 , the pump 140a may be actuated to slow flow into the output channel 130 a thatcorresponds to a different category (category A) than the identifiedcategory B of the incoming particle 222. The slower flow rate in theoutput channel 130 a may cause the particle 212 already in the outputchannel 130 a to continue flowing, but the slower flow rate in theoutput channel 130 a causes the incoming particle 222 to flow into theoutput channel 130 b associated with the identified category B.

Similarly, if the pump 140 a is actuated to stop flow into the outputchannel 130 a that corresponds to a category that is different fromcategory B, the particle 212 already in the output channel 130 a maystop flowing and hold its position within the output channel 130 a. Thestopped flow in the output channel 130 a causes the incoming particle222 to flow into the output channel 130 b associated with the identifiedcategory B of the incoming particle 222 since the flow into the outputchannel 130 b continues to flow.

Finally, if the pump is actuated to reverse the flow in the outputchannel 130 a that corresponds to a category that is different fromcategory B, the particle 212 already in the output channel 130 a mayreverse direction and flow toward the entrance to the output channel 130a. In some examples, an additional sensor may be provided proximate tothe entrance of the output channel 130 a (e.g., at the intersection ofthe output channel 130 a and the input channel 110) to prevent theparticle 212 from going into the input channel 110 or a different outputchannel (e.g., output channel 130 b). The reversed flow in the outputchannel 130 a causes the incoming particle 222 to flow into the outputchannel 130 b associated with the identified category B since the flowinto the output channel 130 b continues to flow in the forwarddirection, as indicated by the arrow in FIG. 6 .

This categorizing process may then continue for subsequent particles 200in the input channel 110. As the particles are sorted into the outputchannels 130 a, 130 b corresponding to the categorization of eachparticle, the particles 200 may be directed into, for example,reservoirs, reaction chambers, or further sorting channels.

In the example system 100 of FIGS. 1-6 , the output channels 130 a, 130b are shown coupled to the input channel 110 in a perpendicularorientation. It will be understood that this manner of coupling isillustrated for schematic purposes and, in various examples, the outputchannels 130 a, 130 b may be coupled to the input channel 110 in anyfeasible orientation. For example, FIG. 7 illustrates an example system700 in which the output channels 730 a, 730 b fork from an input channel710 to form a Y-shape intersection. Of course, a variety of otherarrangements is possible and is contemplated within the scope of thepresent disclosure.

Further, in the example system 100 of FIGS. 1-6 , the input channel 110is coupled to two output channels 130 a, 130 b. In other examples, anexample system may include a larger number of output channels forming atwo-dimensional intersection or a three-dimensional intersection. Forexample, FIG. 8 illustrates an example system 800 in which an inputchannel 810 is coupled to five output channels 830 a-e. Of course, anypractical number of output channels 830 a-e coupled to the input channel810 is possible and is contemplated within the scope of the presentdisclosure.

Referring now to FIG. 9 , another example system for categorizing ofparticles is illustrated. The example system 900 of FIG. 9 is similar tothe example system 100 described above with reference to FIGS. 1-6 andincludes an input channel 910, a sensor 920 and output channels 930 a,930 b. Similar to the example system 100 described above, the examplesystem 900 of FIG. 9 is provided with pumps 940 a, 940 b associated witheach output channel 930 a, 930 b.

The example system 900 of FIG. 9 is further provided with a controller950. The controller 950 is coupled to the sensor 920 and to each pump940 a, 940 b in the output channels 930 a, 930 b. In various examples,the controller 950 may receive signals from the sensor 920, such assignals to indicate detection of a particle in the input channel 910. Invarious examples, the signals from the sensor 920 are indicative ofcategorization of the particle in a selected category of the at leasttwo categories (e.g., category A or category B). In various examples,the signal received by the controller 950 from the sensor 920 mayprovide the category of the detected particle. In other examples, thesignal may provide a characteristic of the detected particle, enablingthe controller 950 to determine the appropriate category of theparticle.

As noted above, the controller 950 of the example system 900 is coupledto each pump 940 a, 940 b corresponding to each output channel 930 a,930 b. Based on the categorization of the particle detected by thesensor 920, the controller 950 may send signals to the appropriatepump(s) 940 a, 940 b to facilitate categorizing or sorting of thedetected particle. For example, as described above with reference toFIGS. 2-6 , the controller 950 may actuate the pump corresponding toeach output channel 930 a, 930 b that is associated with a category thatis different from the category of the detected particle.

Referring now to FIG. 10 , another example system for categorizing ofparticles is illustrated. The example system 1000 of FIG. 10 is similarto the example system 100 described above with reference to FIGS. 1-6and includes an input channel 1010, a sensor 1020 and output channels1030 a, 1030 b. Similar to the example system 100 described above, theexample system 1000 of FIG. 10 is provided with pumps 1040 a, 1040 bassociated with each output channel 1030 a, 1030 b.

In the example system 1000 of FIG. 10 , the flow of particles in theinput channel 1010 is received from a sample source 1050. The samplesource 1050 may be, for example, a reservoir or a reaction chamber whichoutputs the flow of particles 1070. The flow of particles 1070 from thesample source 1050 may contain a density or concentration of particlesthat may be greater than desired for the categorizing process. In thisregard, the example system 1000 of FIG. 10 is provided with a dilutant1060 which is directed to combine with the flow of particles 1070 fromthe sample source 1050. In various examples, the dilutant 1060 may besimilar or identical to the fluid carrying the particles 1070 from thesample source 1050.

The combining of the dilutant 1060 with the flow of particles 1070 fromthe sample source results in a diluted flow of particles 1080 throughthe input channel 1010. In FIG. 10 , the diluted flow of particles 1080is illustrated with increased spacing between the particles. The dilutedflow of particles 1080 can then be sorted as described above withreference to FIGS. 2-6 .

In various examples, as illustrated in the example of FIG. 10 , pumpsmay be provided to control the flow of the sample and the dilutant intothe input channel 1010. In the example of FIG. 10 , a pump 1052 isprovided to control the rate of flow of the sample 1050, and a pump 1062is provided to control the rate of flow of the dilutant 1060. In thisregard, the ratio of sample to dilutant, or the dilution of the sample1050, can be controlled. The pumps 1040 a, 1040 b in the output channels1030 a, 1030 b may facilitate categorizing or sorting of particles, asdescribed above.

Referring now to FIG. 11 , another example system for categorizing ofparticles is illustrated. The example system 1100 of FIG. 11 is similarto the example system 100 described above with reference to FIGS. 1-6and includes an input channel 1110, a sensor 1120 and output channels1130 a, 1130 b. Similar to the example system 100 described above, theexample system 1100 of FIG. 11 is provided with pumps 1140 a, 1140 bassociated with each output channel 1130 a, 1130 b.

As noted above, in some examples, a category of particles may include agroup of types of particles, such as all types of blood cells. In suchcases, it may be desirable to further sort the category of particlesinto at least two subcategories. In this regard, the example system 1100of FIG. 11 includes an output channel sensor 1150 positioned to detectparticles in the output channel 1130 a. The output channel sensor 1150may be provided to categorize particles flowing through the outputchannel 1130 a into one of at least two sub-categories. The examplesystem 1100 further includes at least two sub-output channels 1160 a,1160 b that are coupled to the output channel 1130 a. Thus, thesub-output channels 1160 a, 1160 b are to receive particles from theoutput channel 1130 a. Each sub-output channel 1160 a, 1160 b isassociated with a sub-category. In the example of FIG. 11 , thesub-output channel 1160 a is associated with sub-category A₁, and thesub-output channel 1160 b is associated with sub-category A₂.

In the example system 1100 of FIG. 11 , each sub-output channel 1160 a,1160 b is provided with a corresponding pump 1170 a, 1170 b. The pumps1170 a, 1170 b are operable to selectively slow, stop, or reverse flowof particles into the corresponding sub-output channel 1160 a, 1160 bfrom the output channel 1130 a. Each pump 1170 a, 1170 b is operable,based on the categorization of a detected particle (e.g., by the outputchannel sensor 1150), to selectively slow, stop, or reverse flow ofparticles into the sub-output channel 1160 a, 1160 b from the outputchannel 1130 a. As noted above, actuation of the pumps 1170 a, 1170 bmay be based on categorization of a particle in the output channel 1130a. In the example of FIG. 11 , the sub-output channel 1160 a isassociated with category A₁, and sub-output channel 1160 b is associatedwith category A₂. Thus, if a particle detected by the output channelsensor 1150 is categorized as category A₁, pumps corresponding to allsub-output channels that are associated with a category that isdifferent from category A₁ are actuated. Accordingly, the pump 1170 bcorresponding to sub-output channel 1160 b is actuated. Similarly, if aparticle detected by the output channel sensor 1150 is categorized ascategory A₂, pumps corresponding to all sub-output channels that areassociated with a category that is different from category A₂ areactuated. Accordingly, the pump 1170 a corresponding to sub-outputchannel 1160 a is actuated.

Referring now to FIG. 12 , another example system for categorizing ofparticles is illustrated. The example system 1200 of FIG. 12 is similarto the example system 100 described above with reference to FIGS. 1-6and includes an input channel 1210, a sensor 1220 and output channels1230 a, 1230 b. Similar to the example system 100 described above, theexample system 1200 of FIG. 12 is provided with pumps 1240 a, 1240 bassociated with each output channel 1230 a, 1230 b.

In the example system 1200 of FIG. 12 , output channel sensors 1250 a,1250 b are provided in each output channel 1230 a, 1230 b. The outputchannel sensors 1250 a, 1250 b are provided proximate to the junction ofthe input channel 1210 and the corresponding output channel 1250 a andmay be used to facilitate timing of the actuation of the pumps. In thisregard, the output channel sensors 1250 a, 1250 b may be used to detecta particle sorted for the corresponding channel to ensure that thesorted particle has reached a pre-determined point before the flow inthe channel is stopped, slowed, or reversed for sorting of a subsequentparticle. For example, with reference to FIGS. 5 and 6 , prior toactuation of pump 140 a for sorting of particle 222, a controller maywait for a signal from an output channel sensor, such as output channelsensor 1250 a, that the previous sorted particle 212 has reached apredetermined point within the output channel 130 a or 1230 a.

Referring now to FIG. 13 , another example system for categorizing ofparticles is illustrated. The example system 1300 of FIG. 13 is similarto the example system 100 described above with reference to FIGS. 1-6and includes an input channel 1310, a sensor 1320 and output channels1330 a, 1330 b. In the example system 1300 of FIG. 13 , a single pump1340 may be provided for at least two output channels 1330 a, 1330 b. Invarious examples, a single pump 1340 may be provided for all outputchannels 1330 a, 1330 b. The flow in the output channels 1330 a, 1330 bmay be stopped, slowed, or reversed via the actuation of valves 1350 a,1350 b associated with each output channel 1330 a, 1330 b. In thisregard, in order to stop, slow, or reverse flow in an output channel1330 a, 1330 b, a controller (e.g., the controller 950 of FIG. 9 ) mayopen the valve 1350 a, 1350 b associated with that channel to allow thepump 1340 to flow fluid into the output channel, thus countering theflow from the input channel. In the example system 1300 of FIG. 13 , thepump 1340 may flow fluid from a reservoir 1360 into an output channel1330 a, 1330 b through an open valve (e.g., valves 1350 a, 1350 b). Thefluid in the reservoir 1360 may be a dilutant, buffer, or carrier fluid,for example. In one example, the fluid in the reservoir is a dilutantwhich may facilitate further sub-categorization of particles in anoutput channel, as described above with reference to FIG. 11 .

Referring now to FIG. 14 , a schematic illustration of an example systemfor categorizing of particles is provided. In the example system 1400may be implemented in a microfluidic device, such as those describedabove with reference to FIGS. 1-13 . The example system 1400 includes acontroller 1410. In various examples, the controller 1410 may beimplemented as hardware, software, firmware, or a combination thereof.In one example, the controller 1410 is a processor coupled to orincluding a memory device.

The controller 1410 is coupled to an input channel sensor 1420, such asthe input channel sensors 120, 920, 1020, 1120, 1220, 1320 of thesystems described above with reference to FIGS. 1-13 . As describedabove, the input channel sensor 1420 is provided to detect particlesflowing through an input channel, where the input channel s coupled toat least two output channels to receive particles from the inputchannel. In this regard, the input channel sensor 1420 may providesignals to the controller 1410 indicative of the detection of aparticle.

The controller 1410 of the example system 1400 of FIG. 14 is furthercoupled to a set of pumps 1430. In this regard, the pumps 1430 includepumps corresponding to each of the at least two output channels. Theexample system 1400 is provided for a system with two output channelsand includes two pumps 1432, 1434, each pump 1432, 1434 corresponding toan output channel. As described above, each pump 1432, 1434 is operableto selectively slow, stop, or reverse flow of particles into theassociated output channel from the input channel.

The controller 1410 includes a particle categorization portion 1412 tocategorize a particle detected by the input channel sensor 1420. Invarious examples, the input channel sensor 1420 may send a signal to thecontroller 1410, or the particle categorization portion 1412 of thecontroller 1410, including a characteristic of the detected particle.The particle categorization portion 1412 may use the receivedcharacteristic to categorize the particle into one of a set of at leasttwo categories. Each category in the set of categories corresponds to anoutput channel.

The controller 1410 further includes a pump selection portion 1414 toselectively operate each pump 1432, 1434. In various examples, the pumpselection portion 1414 may select at least one pump for operation basedon the categorization of the particle by the particle categorizationportion 1412. As described above, the pump selection portion 1414 mayoperate a pump corresponding to each output channel not associated withthe category of the detected particle. Thus, flow into each outputchannel associated with a category that is different from the categoryof the detected particle is stopped, slowed, or reversed, causing thedetected particle to be sorted into the remaining output channel.

Referring now to FIG. 15 , a flowchart illustrates an example method forcategorizing particles. The example method 1500 may be implemented in,for example, the controller 1410 of the example system 1400 of FIG. 14or the controller 950 of the example system 900 of FIG. 9 . The examplemethod 1500 includes receiving a signal from an input channel sensorindicative of a detected particle (block 1510). As described above, withreference to FIG. 3 , a particle flowing through an input channel 110may be detected by an input channel sensor 120. The input channel sensor120 may determine at least one characteristic of the detected particleand provide that characteristic in the signal.

At block 1520, the method 1500 includes operating each pump associatedwith an output channel that corresponds to a category that is differentfrom the category of the detected particle. As described above, thedetected particle may be categorized into one of a set of at least twocategories based on the characteristic received from the input channelsensor. Each category in the set of categories corresponds to an outputchannel. Based on the categorization of the detected particle, the pumpassociated with each output channel that corresponds to a category thatis different from the category of the detected particle is activated tostop, slow, or reverse flow in that/those output channels. Thus, flow ofthe detected particle is directed to the appropriate output channel.

Referring now to FIG. 16 , a block diagram of an example system isillustrated with a non-transitory computer-readable storage mediumincluding instructions executable by a processor for particlecategorizing. The system 1600 includes a processor 1610 and anon-transitory computer-readable storage medium 1620. Thecomputer-readable storage medium 1620 includes example instructions1621-1622 executable by the processor 1610 to perform variousfunctionalities described herein. In various examples, thenon-transitory computer-readable storage medium 1620 may be any of avariety of storage devices including, but not limited to, a randomaccess memory (RAM) a dynamic RAM (DRAM), static RAM (SRAM), flashmemory, read-only memory (ROM), programmable ROM (PROM), electricallyerasable PROM (EEPROM), or the like. In various examples, the processor1610 may be a general purpose processor, special purpose logic, or thelike.

The example instructions include identify a selected category of adetected particle instructions 1621. In this regard, based on a signalfrom a sensor in an input channel, a detected particle may becategorized into the selected category from at least two categories. Asdescribed above, the input channel is coupled to at least two outputchannels, each output channel being associated with a category from theat least two categories.

The example instructions further include operate a pump associated witheach output channel associated with a category that is different fromthe selected category of the detected particle instructions 1622. Asdescribed above, pumps corresponding to each output channel associatedwith a category that is different from the selected category of thedetected particle may be operated to slow, stop, or reverse flow ofparticles into the associated output channel from the input channel.Thus, the detected particle may be sorted into the appropriate channels.

Software implementations of various examples can be accomplished withstandard programming techniques with rule-based logic and other logic toaccomplish various database searching steps or processes, correlationsteps or processes, comparison steps or processes and decision steps orprocesses.

The foregoing description of various examples has been presented forpurposes of illustration and description. The foregoing description isnot intended to be exhaustive or limiting to the examples disclosed, andmodifications and variations are possible in light of the aboveteachings or may be acquired from practice of various examples. Theexamples discussed herein were chosen and described in order to explainthe principles and the nature of various examples of the presentdisclosure and its practical application to enable one skilled in theart to utilize the present disclosure in various examples and withvarious modifications as are suited to the particular use contemplated.The features of the examples described herein may be combined in allpossible combinations of methods, apparatus, modules, systems, andcomputer program products.

It is also noted herein that while the above describes examples, thesedescriptions should not be viewed in a limiting sense. Rather, there areseveral variations and modifications which may be made without departingfrom the scope as defined in the appended claims.

What is claimed is:
 1. A system, comprising: an input channel having afirst end and a second end to receive particles through the first end; asensor to categorize particles in the input channel into one of at leasttwo categories; at least two output channels, each output channelfluidically coupled to the second end of the input channel to receiveparticles from the input channel, each output channel being associatedwith at least one category of the at least two categories, each outputchannel having a corresponding pump operable, based on thecategorization of a detected particle in a category associated with adifferent output channel, to selectively stop or reverse a flow ofparticles into the output channel from the input channel, wherein thecorresponding pump is disposed in an asymmetric position within theassociated output channel, the asymmetric position being distal from thesecond end of the input channel.
 2. The system of claim 1, furthercomprising a controller coupled to the sensor and to each pump, thecontroller to: receive a signal from the sensor indicative ofcategorization of a particle in a selected category of the at least twocategories; and selectively actuate each pump corresponding to an outputchannel that is associated with a different category than the selectedcategory.
 3. The system of claim 1, wherein the input channel and eachoutput channel are microfluidic channels.
 4. The system of claim 3,wherein each pump is an inertial pump integrated within a correspondingmicrofluidic channel.
 5. The system of claim 1, further comprising: anoutput channel sensor corresponding to at least one of the at least twooutput channels.
 6. The system of claim 5, wherein the output channelsensor is to categorize particles in a first output channel of the atleast two output channels into one of at least two sub-categories, thefirst output channel having an inlet end and an outlet end, the inletend of the first output channel being fluidically coupled to the secondend of the input channel; the system further comprising: at least twosub-output channels, each sub-output channel fluidically coupled to theoutlet end of the first output channel to receive particles from thefirst output channel, each sub-output channel being associated with atleast one sub-category of the at least two sub-categories, eachsub-output channel having a corresponding pump operable, based on thecategorization of a detected particle in the first output channel in acategory associated with a different sub-output channel, to selectivelyslow, stop, or reverse a flow of particles into the sub-output channelfrom the first output channel.
 7. A system, comprising: an input channelsensor to detect particles in an input channel, the input channel havinga first end and a second end and being fluidically coupled to at leasttwo output channels at the second end, each output channel to receiveparticles from the input channel; a pump associated with each of the atleast two output channels, each pump being operable to selectively stopor reverse flow of particles into the associated output channel from theinput channel, wherein the pump is disposed in an asymmetric positionwithin the associated output channel, the asymmetric position beingdistal from the second end of the input channel; and a controller,comprising: a particle categorization portion to categorize a particledetected by the input channel sensor into an identified categoryselected from at least two categories, each category of the at least twocategories being associated with a separate output channel of the atleast two output channels; and a pump selection portion to operate eachpump corresponding to an output channel that is associated with adifferent category than the identified category.
 8. The system of claim7, wherein the input channel and each output channel are microfluidicchannels.
 9. The system of claim 8, wherein each pump is an inertialpump integrated within a corresponding channel.
 10. The system of claim7, further comprising: an output channel sensor to detect particlesflowing through a first output channel of the at least two outputchannels, the first output channel being coupled to at least twosub-output channels to receive particles from the first output channel;a sub-output pump associated with each of the at least two sub-outputchannels, each pump being operable to selectively slow, stop, or reverseflow of particles into the associated sub-output channel from the firstoutput channel, wherein the particle categorization portion is tocategorize a particle detected by the output channel sensor into anidentified sub-category selected from at least two sub-categories, eachsub-category of the at least two sub-categories being associated with asub-output channel of the at least two sub-output channels; and whereinthe pump selection portion is to operate each sub-output pumpcorresponding to a sub-output channel that is associated with adifferent sub-category than the identified sub-category.
 11. The systemof claim 7, further comprising: an output channel sensor correspondingto each of the at least two output channels.
 12. A non-transitorycomputer-readable storage medium encoded with instructions executable bya processor of a computing system, the computer-readable storage mediumcomprising instructions to: identify a selected category of a particlefrom at least two categories based on a signal from a sensor in an inputchannel, the input channel being fluidically coupled to at least twooutput channels, each output channel being associated with a categoryfrom the at least two categories; and operate a pump associated witheach output channel associated with a different category than theselected category of the detected particle to stop or reverse a flow ofparticles into the associated output channel from the input channel,wherein the pump is disposed in an asymmetric position within theassociated output channel, the asymmetric position being distal from thefluidic couple of the associated output channel and the input channel.13. The non-transitory computer-readable storage medium of claim 12,wherein the input channel and each output channel are microfluidicchannels.
 14. The non-transitory computer-readable storage medium ofclaim 13, wherein each pump is an inertial pump provided within acorresponding channel.
 15. The non-transitory computer-readable storagemedium of claim 12, the computer-readable storage medium furthercomprising instructions to: identify a selected sub-category of aparticle from at least two sub-categories based on a signal from anoutput channel sensor in at least one output channel, the output channelbeing fluidically coupled to at least two sub-output channels, eachsub-output channel being associated with a sub-category from the atleast two sub-categories; and operate a pump associated with eachsub-output channel associated with a sub-category that is different fromthe selected sub-category of the detected particle to slow, stop, orreverse a flow of particles into the associated sub-output channel fromthe output channel.
 16. The system of claim 1, wherein each pump is aninertial pump including a thermal actuator.
 17. The system of claim 1,wherein each pump includes a piezo-electric membrane.
 18. Thenon-transitory computer-readable storage medium of claim 12, includinginstructions to, based on the signal from the sensor, selectivelyactuate the pump associated with the different category than theselected category to direct a flow of the particle.
 19. Thenon-transitory computer-readable storage medium of claim 15, includinginstructions to, based on the signal from the output channel sensor,selectively actuate the pump associated with the sub-output channel todirect a flow of the particle.
 20. The system of claim 5, wherein thecorresponding pump being operable, based on detection of the particle inthe output channel, to selectively stop or reverse a flow of theparticle in the output channel; or wherein the output channel sensor isproximate the second end of the input channel; or a combination thereof.